The invention relates to an implant for the transforaminal interbody fusion of lumbar vertebral column segments, wherein at least some sections of the surface areas coming into direct contact with the vertebral column are provided with a dislocation protection, wherein further an engagement part for a positioning instrument is provided in or on the implant, and holes or hollow spaces are disposed in the implant for filling purposes.
Attempts are made to use minimal invasive surgery for spine operations. To this end, so-called PLIF (posterior lateral interbody fusion) operation techniques were developed. According to such an operation technique the intervertebral disc is removed through a posterior access, and the intervertebral space is filled with autologous bone. This technique is based on Cloward, who was the first to carry through such an operation in 1943. Further developments of the PLIF technique resulted in the application of a transforaminal access. This technique provides for the dorsal, transforaminal introduction of titanium cups—so-called cages—which are filled with autologous cancellous bone. At the same time, a dorsal instrumentation and stabilization is applied. The advantage of the briefly outlined method is that no transabdominal or retroperitoneal additional access has to be used.
The “Biotit Cage” of the company Ulrich serves to replace an intervertebral disc of the lumbar vertebral column. The cage is inserted through a dorsal access, with the application being possible in pairs or individually. This prior cage is substantially U-shaped and comprises a dislocation protection in the form of a striated structure. The implant material of the aforementioned cage is titanium or a titanium alloy, respectively, so that relatively large radiological windows are necessary to control the fusion.
Further known is a cage distributed by the company Stryker Orthopaedic, U.S.A., which is a cubic implant and can be implanted in pairs into the intervertebral space by an anterior as well as a posterior approach.
As regards the prior art, reference is additionally made to DE 43 28 062 A1, which relates to an implant for the replacement of vertebral bodies and/or the stabilization and fixation of the vertebral column. This implant consists of an implant body which is pushed onto a support rod transversely to the axis of the rod. The implant body according to DE 43 28 062 A1 is provided with a surface structure bearing against the vertebral bodies adjacent to the implant, so as to achieve a mutual fixation of the adjacent surfaces of the implant body on the one hand and the vertebral body on the other hand.
The prior art likewise includes height-adjustable vertebral body implants for the replacement of one or more vertebral bodies, e.g. according to DE 44 23 257 A1, DE 195 19 101 A1 or DE 195 09 317 A1. However, the production of these height-adjustable implants is very expensive, and their handling is complicated.
In the German utility model DE 296 16 778 U1 a vertebral body replacement is disclosed, which is inserted, for example, after a vertebral body resection to replace the missing vertebral body. Such replacements are made of a body-compatible material, with the front ends forming an irregular edge and the wall of the replacement having holes to provide for enough space to receive bone substance.
To insert the replacement according to DE 296 16 778 U1, a tool having a relatively long shank is used, with the shank having a threaded journal on the free end thereof to be brought into engagement with a threaded hole of the sleeve-shaped body so as to insert the same into the space of the resected vertebral body, in the predefined position between two adjacent vertebral bodies.